Heating, ventilation, and/or air conditioning (HVAC) systems are commonly used to control the comfort level within a building or other structure. There are various types of HVAC systems that are in use today. Some HVAC systems affect conditions in multiple rooms of a building with a centralized source of heated or cooled air (e.g., central furnace, air conditioner and/or air handler) and a network of ducts, dampers, etc., to manage airflow throughout the building. Other HVAC systems are more limited in extent, such as self-contained window air conditioner. Some HVAC systems, such as mini-split HVAC systems, include an indoor unit that circulates cooled and/or heated air inside a room of the building without a network of ducts, and an outdoor unit connected to the indoor unit via lines carrying a working fluid that transfers heat between the indoor unit and the outdoor unit.
Many HVAC systems include a controller that activates and deactivates one or more HVAC units or components of the HVAC system to affect and control one or more environmental conditions within the building. These environmental conditions can include, but are not limited to, temperature, humidity, and/or ventilation. In many cases, such an HVAC controller may include, or have access to, one or more sensors, and may use parameters provided by the one or more sensors to control the one or more HVAC components to achieve desired programmed or set environmental conditions.
An HVAC controller may be equipped with a user interface that allows a user to monitor and adjust the environmental conditions at one or more locations within the building. With more modern designs, the interface typically includes a display panel, such as a liquid crystal display panel, inset within a housing that contains a microprocessor as well as other components of the HVAC controller. In some designs, the user interface may permit the user to program the controller to control to a certain schedule that is determined by the user. For example, the interface may include a routine that permits the user to set the desired temperature at one or more times during a particular day and/or group of days. In many cases, such a programmable schedule may help reduce energy consumption of the HVAC system by changing the setpoint to an energy saving set back temperature during certain times, such as when the building or space is expected to be unoccupied or when the occupants are expected to be sleeping.